In an RCA washing step in which semiconductor wafers are washed, foreign substances attached to a semiconductor wafer are removed by using chemicals. In the RCA washing step, the chemicals to be used varies depending on the treatment. For example, when particles attached to a semiconductor wafer are removed, an ammonium hydroxide/hydrogen peroxide mixture is used; whereas when metal ions attached to a semiconductor wafer are removed, a hydrochloric acid/hydrogen peroxide mixture is used. When the semiconductor wafers are washed with the chemicals such as the ammonium hydroxide/hydrogen peroxide mixture or hydrochloric acid/hydrogen peroxide mixture, it is necessary to raise the temperature of the chemicals used for washing to, for example, approximately 80° C.
Conventionally, for controlling the temperature of the chemicals, the chemicals are heated by using a fluid heating device, thereby raising the temperature of the chemicals. The fluid heating device heats the chemicals by using, for example, a lamp heater such as a halogen lamp and by bringing a quartz glass tube into contact with the chemicals while electric current is applied to the lamp heater that has been put into the quartz glass tube, thereby heating the solution (see, for example, Patent Document 1).
When the lamp heater (the halogen lamp) is used as a heat source and the intended chemicals described above are treated in the fluid heating device, radiation (emission) performs 90% or more of heating. In addition, because the radiation heating can have a very high heating capacity per unit area, it is possible to make the device smaller.